A conventional headset assembly is show in FIG. 5 and includes an upper part 10 mounted to the upper end of a head tube 30 through which a steerer tube (not shown) extends and a lower part 20 connected to the lower end of the head tube 30. The upper part 10 includes an upper race 11 inserted into the upper end of the head tube 30 and has a first groove 112 defined in an upper portion thereof, an upper cap 12 thread mounted to the steerer tube and has a second groove 122 defined in the lower portion thereof, and a bearing 13 received between the first groove 112 and the second groove 122. The lower part 20 has a similar structure to that of the upper part 10 and includes a lower race 21 inserted into the lower end of the head tube 30 and has a third groove 212, a lower cap 22 with a fourth groove 222, and a bearing 23 received between the third groove 212 and the fourth groove 222. The surface of the upper cap 12 has to be heat treated so as to have sufficient hardness so as to bear balls of the first bearing 13 rolling thereon. However, the upper cap 12 tends to be deformed by the process of heat treatment such that the first bearing 13 cannot operate properly and thus shortens the term of usage of the first bearing 13. Furthermore, the inner threaded portion of the upper cap can 12 be heat treated, and this could affect the shape thereof. The process of heat treatment is necessary for the upper cap 12, but it also produces many problems, such as, the deformation of the upper cap 12, a fatigue problem with the upper cap 12 and high manufacturing cost. The same problems are also found on the lower cap 22.
In addition, the bearing 13/23 includes an annular cage 132 in which a plurality of ball bearings are retained and separated so as to prevent the ball bearings from dropping from the first and the second groove 112, 122. However, because of the cage 132, the bearing assembly 13/23 typically has only 16 ball bearings in the cage 132, and this is deemed not to be enough. The bearing assembly 13/23 has a specification orientation to be used, but assemblers could set the bearing 13/23 in the wrong orientation, such as the orientation shown in FIG. 6.
The present invention intends to provide a headset for a bicycle comprising an annular member disposed between the bearing and the upper/lower race and a flange extending from the upper/lower cap member so as to retain the corresponding annular track so that the cap member does not need to be heat treated. The present invention therefore effectively mitigates and/or obviates the problems of the conventional headset assembly.